1. Field of the Invention
The present invention relates to a porous sheet and a method for manufacturing the porous sheet, and more particularly, to a porous sheet that is capable of being used in processes such as suction peeling and vacuum suction fixing in manufacture of a glass substrate for liquid crystal, a semiconductor wafer, or a multilayer ceramic capacitor.
2. Description of the Related Art
In general, peeling of a ceramic green sheet is performed by vacuum, and peeling force is changed according to the shape of a structure that can suck the ceramic green sheet by vacuum.
In the prior art, a metal body or a sintered metal body having surface holes in a portion in contact with a ceramic green sheet in a vacuum is used or a metal plate in which holes are formed at regular intervals by etching is used.
However, since a peeling mold is formed of a metal body, there is a problem that a contact portion of the ceramic green sheet is damaged. Further, there is a problem that the ceramic green sheet is damaged by holes formed in the peeling mold.
Like this, when a surface of the ceramic green sheet for manufacturing a multilayer ceramic capacitor is damaged, an internal pattern formed on the surface of the ceramic green sheet is damaged and thus it may cause product defects such as a short after lamination.
Accordingly, studies on a porous suction sheet, which can easily peel a ceramic green sheet with strong suction force without damaging the ceramic green sheet, have been continuously made. Currently, a porous sheet, that is, a porous ultrahigh molecular weight polyethylene sheet attached to a peeling mold having fine holes has been applied to peeling and lamination processes of the multilayer ceramic capacitor. This technology is disclosed in Patent Document 1.
FIG. 1 is a scanning electron microscope photograph of a cross section of a porous sheet disclosed in the Patent Document 1.
A porous ultrahigh molecular weight polyethylene sheet is manufactured by sintering ultrahigh molecular weight polyethylene powder using heated vapor and cooling and cutting the sintered body, and it is possible to manufacture a sheet with a relatively large thickness and improve surface roughness, coefficient of friction, rigidity, and so on according to manufacturing processes.
Referring to FIG. 1, it is possible to check that the porous sheet is made of particulate ultrahigh molecular weight polyethylene powder.
However, since this porous ultrahigh molecular weight polyethylene sheet has problems such as high manufacturing costs in manufacturing processes, variation between lots and between products, and difficulty in reducing the size of pores for securing porosity, it is difficult to cope with thinning of products.